Propeller 4 or 5 blade

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dartman

Seaman Apprentice
Joined
Oct 12, 2003
Messages
47
I have a 150 Johnson on a Cape Horn boat, and I have a little problem with ventilation while turning. The ventilation plate is 1" above the bottom of keel and cannot be lowered further. I have a 19" pitch Viper prop now. Will a four or five blade prop help this situation? Would a change in pitch be required? What is a recommended prop brand and model? Thanks
 
D

dartman

Seaman Apprentice
Joined
Oct 12, 2003
Messages
47
Re: Propeller 4 or 5 blade

Any relavant comments are appreciated.
 
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AUGIDAWG

Petty Officer 2nd Class
Joined
Oct 31, 2002
Messages
189
Re: Propeller 4 or 5 blade

My boat with a 200 Johnson with the stock 3 blade would ventilate badly when turning.<br />I went to a four blade and now it doesn't ventilate at all.
 
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walleyehed

Admiral
Joined
Jun 29, 2003
Messages
6,767
Re: Propeller 4 or 5 blade

Alot of the reason for the ventilation Change is because the blade design changes-going from 3 to 4 blades.<br />How far aft is your engine mounted? It sounds as though you need to go back some....also, a prop that may suit your set-up better, would be a 20" RAKER. The Raker bites better than the Viper in most situations.<br /> A high-quality 4-blade may help however, I think there are other options available in 3-blade that would not cost you any speed, and again, another 2 inches of setback may fix your problem, depending on where you are now demension-wise..... :)
 
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clintg

Recruit
Joined
Nov 2, 2003
Messages
3
Re: Propeller 4 or 5 blade

AUGIDAWG<br /><br />What brand and model 3 and 4 blade prop did you use?
 
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AUGIDAWG

Petty Officer 2nd Class
Joined
Oct 31, 2002
Messages
189
Re: Propeller 4 or 5 blade

I originally had the ventilation problem with the OMC aluminum 3 blade 14.25" x 19". It was in perfect condition.<br /><br />I went to the Turbo Ultra 4 blade stainless, 14.25" x 17".<br /><br />I lost about 2 mph on the top end, but now it revs to 6000 rpm instead of 5700, jumps out of the water during the hole shot, and doesn't ventilate unless I am trimmed too far out and crank a turn.<br /><br />I used to ventilate when trimmed down and just a slight turn.
 
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backdraft

Petty Officer 1st Class
Joined
Dec 29, 2002
Messages
266
Re: Propeller 4 or 5 blade

Sometimes a venting problem can be cured by double cupping the prop. This causes the water to hang on the prop longer increasing thrust. Also another cause is the prop is being aeriated in the turn by a rough bottom or the leading edge of the prop is surfacing , catching air in the turns.Just a few point to ponder. <br />A four blade stainless is an outstanding prop . nevjb
 
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